Input (part 1: devices)

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Input (part 1 devices)
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Where we are...

• Two largest aspects of building interactive
  systems output and input
• Have looked at basics of output
• Now look at input

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Input

• Generally, input is somewhat harder than output
• Less uniformity, more of a moving target
• More affected by human properties
• Not as mature
• Will start with low level (devices) and work up
  to higher level

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Input devices

• Keyboard
• Ubiquitous, but somewhat boring
• Quite mature design
• QWERTY key layout
• Where did it come from?

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QWERTY key layout

• Originally designed to spread out likely adjacent
  key presses to overcome jamming problem of very
  early mechanical typewriters
• Often quoted as intentionally slowing down
  typing, but thats not true

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QWERTY keyboard layout

• Other layouts have been proposed
• Dvorak is best known
• Widely seen as better
• Experimental and theoretical evidence casts doubt
  on this
• Alternating hands of QWERTY are a win since
  fingers move in parallel

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QWERTY keyboard layout

• Whether or not Dvorak layout is better, it did
  not displace QWERTY
• Lesson once there is sufficient critical mass
  for a standard it is nearly impossible to
  dislodge (even if there is an apparently good
  reason to do so)

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Keyboards

• Repetitive Stress Injury
• First comes up here, mouse tends to be a little
  worse for most people
• Take this seriously for yourself!
• Can be a VERY bit deal
• Biggest thing adjust your work environment (e.g.
  chair height)

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Buttons

• Similar to keyboard, but not for typing letters
  but for symbols
• separate collection of keys with typically same
  form but different purpose
• now see as function keys that come standard
  with keyboards
• also show up on e.g., mouse

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Buttons

• Buttons often bound to particular commands
• e.g., function keys
• Improved quite a bit with labels
• Software changeable labels would be ideal, but we
  dont typically get this

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Valuators

• Returns a single value in range
• Major impl. alternatives
• Potentiometer (variable resistor)
• similar to typical volume control
• Shaft encoders
• sense incremental movements
• Differences?

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Valuator alternatives

• Potentiometer
• normally bounded range of physical movement
  (hence bounded range of input values)
• Keeps residual position in device
• Shaft encoder
• Unbounded range of movement
• No residual position in device

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Locators (AKA pointing devices)

• Returns a location (point)
• two values in ranges
• usually screen position
• Examples
• Mice (current defacto standard)
• Track balls, joysticks, tablets, touch panels,
  etc.

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Locators

• Two major categories
• Absolute vs. Relative locators

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Absolute locators

• One-to-one mapping from device movement to input
• e.g., tablet
• Faster
• Easier to develop motor skills
• Doesnt scale past fixed distances
• bounded input range
• less accurate (for same range of physical
  movement)

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Relative locators

• Maps movement into rate of change of input
• e.g., joystick (or TrackPoint)

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Relative locators

• More accurate (for same range of movement)
• Harder to develop motor skills
• Not bounded (can handle infinite moves)

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Q is a mouse a relative or absolute locator?
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Q is a mouse a relative or absolute locator?

• Answer No
• Third major type Clutched absolute
• Within a range its absolute
• Can disengage movement (pick it up) to extend
  beyond range
• picking up clutch mechanism

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Clutched absolute locators

• Very good compromise
• Get one-to-one mapping when in range (easy to
  learn, fast, etc.)
• Clutch gives some of benefits of a relative
  device (e.g., unbounded)
• Trackballs also fall into this category

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Device specifics joysticks

• self centering
• relative device
• possible to have absolute joysticks, but scaling
  is bad

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Joystick construction

• Two potentiometers
• x and y
• resistance is a function of position

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Joystick construction

• Two potentiometers
• x and y
• resistance is a function of position

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Joystick construction

• TrackPoint (IBM technology)
• uses strain gauge sensors
• Also can be implemented with switches
• one in each direction
• Fixed speed of movement

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Trackballs

• (Typically large) ball which rolls over 2 wheels

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Trackballs

• Clutched absolute
• but with small movement range
• Infinite input range, etc.
• Properties vary quite a bit
• scaling of movements
• mass of ball
• high mass ball can act as a relative device by
  spinning it

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Mouse

• Clutched absolute
• infinite range, etc.
• How is it constructed?

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Mouse

• Clutched absolute
• infinite range, etc.
• How is it constructed?
• Turn a trackball upside down

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Mouse

• Current dominant device
• so much so that some people call any pointing
  device a mouse
• overall a very good device

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Mouse

• Invented by Douglas Engelbart et al. 1967
• http//sloan.stanford.edu/MouseSite/Archive/Augmen
  tingHumanIntellect62/Display1967.html

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Touch panel

• What kind of a device?

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Touch panel

• Absolute device
• Possible to do input and output together in one
  place
• actually point at things on the screen
• Resolution limited by size of finger (digital
  input)
• Or requires a pen

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Touch panel construction

• Membrane
• resistive, fine wire mesh
• Capacitive
• Optical
• finger breaks light beam
• Surface acoustic waves

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Drawing tablet

• Absolute or relative?

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Drawing tablet

• Absolute device
• Normally used with pen / stylus
• Allows real drawing (try drawing with a mouse
  vs. a pen)
• Can often trace over paper images

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Construction of drawing tablet

• Traditional (Rand) tablet
• middle 60s
• grid of wires (100 / inch)
• each wire transmits binary of its coord
• stylus picks up closest
• Can also make pen transmitter and tablet receiver

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Drawing tablet details

• Typically have tip switch
• May also have switch(es) on side of stylus
• Can also support a puck with buttons
• Best current devices can support multiple pens
  at the same time and sense rotation of a puck

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Alternate Approaches to Tablets

• Old acoustic (sort of a fun device)
• stylus emits spark
• strip microphones at edge of tablet
• difference in arrival time of sound

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Interesting device Virtual Ink Mimio

• Updated acoustic tablet
• recording whiteboard
• ultrasonic chirps
• 100dpi resolution over 8ft

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3D locators

• Can extend locators to 3 inputs
• Some fun older devices
• 3D acoustic tablet
• Wand on reels
• Multi-axis joystick

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3D locators

• Typical for VR use Polhemus
• 6D device (x,y,z pitch, roll, yaw)
• Magnetic sensing technology
• Doesnt work well near metal
• Doesnt work well near deflection coils of CRT

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Light pen (a very old device)

• A pick device
• returns ID of an object on the screen (not a
  position)
• For vector refresh displays
• Vector refresh worked with small display list
  processor
• Add register holding current obj ID
• Photocell causes interrupt when beam passes (grab
  and return ID)

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Light pen (a very old device)

• Cant really do this anymore
• on raster display light pen is just a locator
• But its conceptually what we usually want for
  input what object the user is pointing at
• We will simulate in SW (picking)

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Lots of other devices

• Still mostly KB mouse, but increasing diversity
  
• Cameras!
• Lots of untapped potential in vision
• Microphones
• speech as data
• speech recognition

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Lots of other devices

• Any favorites?

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Some interesting ones I know about

• Thumb Wheel
• DataGlove
• Motion detectors (and other sensors)
• Accelerometers
• Fingerprint readers
• RF tags (physical objects as tokens for
  data/action)
• Sub-gram resolution scales

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